A. Technical Field
The present invention relates generally to semiconductor processing and semiconductor processing apparatus and more particularly to improvements in the efficiency in the use and operation of semiconductor processing apparatus.
B. Background of the Invention
There is an initiated and ongoing trend in the development of semiconductor processing apparatus, particularly to improve their efficiency of operation and operate more “green” with less detrimental effects on the environment. That trend includes steps of going more “green” in the operation of such apparatus, such as, reducing the power consumption of the apparatus and reducing the required time and the amount of expense necessary to clean the apparatus between production runs. Examples of such apparatus are the heat treatment and deposition of various kinds of materials and/or layers on a workpiece, which may be a semiconductor wafer or any other type, and kind of substrate to be heated, treated and/or deposited with different types of film. The process employed for heat treatment is generally annealing of the workpiece as known in the art. The processes employed for depositing film layers may be, for example, chemical vapor deposition (CVD), physical vapor deposition (PVD) and plasma-enhanced chemical vapor deposition (PECVD) as known in the art. A particular CVD process used extensively today is the deposition of tungsten films on a workpiece, such as, for example, from a gas-entrained constituent comprising tungsten hexafluoride (WF4). These kinds of semiconductor processing apparatus are generally run continuously until required maintenance becomes necessary and production must cease and the apparatus is cleaned with a dry or wet cleaning gas process or the apparatus chamber is opened for extensive cleaning of it interior.
Some of the problems being sought to be solved at the present time are the prevention of corrosion and depletion of the workpiece platen assembly and heater surfaces caused by repeated cleanings, and the reduction of undesired depositions from deposition gases on surfaces of the apparatus chamber, including the pedestal assembly for the workpiece, which depositions can affect the operation of the apparatus and can result in frequent cleaning of surfaces exposed to these unwanted depositions within the chamber. In most cases, these undesired depositions are on the chamber walls of the apparatus as well as exposed surfaces of the pedestal assembly and its stem within the chamber. These unwanted depositions also include poorly bonded depositions on pedestal surfaces, which may readily flake off and may cause defects in the workpiece. Moreover, these depositions can affect the formation of the plasma in the chamber causing uneven deposition of a deposited film on the workpiece and may degrade the operation of components in the apparatus chamber. Even in the case of heat treatment of workpieces, such as in annealing where no film deposition is involved, poorly bonded depositions on chamber components may become more active due to high chamber temperatures and become dislodged and, possibly, contaminate the workpiece undergoing treatment. Thus, it is necessary to provide frequent cleaning of the apparatus chamber, which requires the stopping of workpiece production and the passing of a cleaning gas through the chamber that provides reactant species that react with the undesired depositions and etch away the depositions from the chamber or pedestal/stem surfaces that are then exhausted and removed from the chamber. Also, periodically, it is necessary to open the chamber and accomplish a more thorough cleaning of chamber walls and component surfaces exposed to deposition gases flowing through the apparatus. Thus, cleaning time becomes a major factor in reducing the total time of operating the apparatus in the production of workpiece output. What is needed are ways of increasing the workpiece production output and decreasing the time spent cleaning the apparatus chamber and pedestal assembly thereby increasing the overall rate of workpiece output production per month.
Many apparatus have platen surfaces on heaters where the heater bodies are made of aluminum, although some may be made of ceramics. These types of heater bodies are resistant to the corrosive effect of deposition gases. However, the heater surfaces are etched away during the cleaning of the apparatus in the process of removing unwanted depositions that may be on its surfaces. Thus, over time, it becomes necessary to replace the heater. What is desired, then, is to reduce or eliminate this undesired etching away of the metal heater body and, further, provide a replacement heater for existing semiconductor processing apparatus that is more resistant to undesired etching away of the metal heater body over time during the chamber cleaning processes.
In summary, what is needed is an improvement to workpiece production rate in continuously operated semiconductor processing equipment by reducing the amount of time required to clean the apparatus chamber which, in turn, will also reduce the amount of consumables required in the cleaning process, resulting in a “greener” operating apparatus.